The present invention relates to fuel injection pumps of the type having a pump rotor with a pumping chamber with one or more radially extending pumping plunger bores, a pumping plunger mounted in each plunger bore, annular cam means surrounding the pump rotor for reciprocating the pumping plungers for supplying intake charges of fuel to the pumping chamber and periodically delivering charges of fuel from the pumping chamber at high pressure for fuel injection, and a distributor head with a plurality of distributor outlets, the pump rotor being rotatably mounted within the distributor head and forming a distributor rotor with one or more distributor ports for distributing the high pressure charges of fuel to the plurality of distributor outlets in sequence (such fuel injection pumps being referred to herein as "Rotary Distributor Type Fuel Injection Pumps").
The high pressures within such Rotary Distributor Type Fuel Injection Pumps present certain operating problems as follows:
(a) a large axial force on the rotor thrust bearing causes galling and eventually mechanical failure of the thrust bearing; and PA1 (b) high pressure pulsations subject certain portions of the pump rotor to a large cyclical stress, resulting in crack initiation, crack propagation and eventually pump rotor failure. PA1 (a) during pump operation, particularly at high speed and during rapid acceleration, a substantial amount of heat is generated by the thin layer of fuel lubricant between the relatively rotating surfaces of the distributor rotor and distributor head; PA1 (b) adequate lubrication of the relatively rotating surfaces is difficult to achieve at high speed and high temperature, particularly with low viscosity fuels such as gasoline and methanol; and PA1 (c) the thermal expansion of the outer diameter of the distributor rotor and inner diameter of the distributor head must occur at approximately the same rate throughout the full range of operation of the pump and particularly during cold starting and rapid acceleration; otherwise, the resulting unequal thermal expansion of the parts will cause inadequate lubrication and rotor seizure. PA1 (a) high speed electromagnetic operation of the valve member; PA1 (b) a precise open limit position of the valve member; PA1 (c) controlled spring actuation of the valve member to prevent valve member bounce; PA1 (d) improved valve responsiveness; and PA1 (e) low valve wear and long useful valve life.
Additionally, because the fuel charges are distributed at high pressure, the relatively rotating surfaces of the distributor head and distributor rotor are required to have a very precise rotational fit (for example, a diametral clearance of 80-100 millionths of an inch) to ensure adequate sealing and lubrication. The precise rotational fit presents certain operating problems as follows:
A principal aim of the present invention is to provide a new and improved Rotary Distributor Type Fuel Injection Pump which alleviates the above described operating problems presented by the high pressures within the pump and the precise rotational fit between the distributor head and distributor rotor.
Another aim of the present invention is to provide in a Rotary Distributor Type Fuel Injection Pump of the type having a valve member coaxially mounted within the pump rotor, a new and improved valve operating mechanism which provides one or more of the following advantages:
In accordance with another aim of the present invention, a new and improved Rotary Distributor Type Fuel Injection Pump is provided which (a) can deliver high pressure charges of fuel from the pumping chamber at 12,000 psi and higher; (b) can be used with high speed engines; and (c) can be electrically controlled to precisely regulate the size and timing of the injected fuel charge.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
A better understanding of the invention will be obtained from the following detailed description and accompanying drawings of an illustrative application of the invention.